Which are the oldest and newest parts of Windsor castle?

The oldest part of Windsor Castle is the Round Tower, which was begun by Henry II in 1170. It is a massive, stone keep that was used as a royal residence and a place of refuge in times of danger.

Newest part of Windsor Castle:

The newest part of Windsor Castle is the State Apartments, which were built by George III and Queen Charlotte in the late 18th century. The State Apartments are a series of richly decorated rooms that are used for official functions, such as state dinners and receptions.